Digital video and audio consumer electronics/devices are used by consumers to receive and conduct numerous services and transactions, for example, to receive video, audio and data streams from a (cable television) service provider, such as Emergency Alerting, Interactive Program Guides, Impulse Pay-Per-View (IPPV), Video On Demand (VOD), General Messaging, and Interactive Services.
In particular, one such device is a point of deployment (POD) module. A POD module is a removable card inserted into a host device, such as a set-top box. As is well known in the art, a POD module provides several functions including security that is physically separate from a set-top box's navigation function and processing out-of-band cable signals. For additional details on POD modules, see SOCIETY OF CABLE TELECOMMUNICATIONS ENGINEERS, INC. (SCTE) Document: SCTE DVS 131 Rev. 7, entitled “Draft Point-of-Deployment (POD) Module Interface Proposal” dated Dec. 3, 1998, (hereinafter known as “DVS131r7”).
Consumers rely on such devices to communicate, access programs and services or engage in commercial transactions in which privacy and/or security is desired and, in many cases, expected. In this regard, the POD module also decrypts content information encrypted by service providers. It may be part of a so-called “conditional access” (CA) system that spans the head-end of a service provider network and the POD module itself.
To receive information from a particular service provider, a POD module that contains an algorithm related to a particular proprietary CA system, which is associated with a particular service provider, must be inserted to a host device. After content information is selected by the host device/viewer and received in the POD module from a service provider, it is decrypted in the POD module. The (decrypted) content information is again encrypted in the POD module with a new set of keys to protect it when transmitted across the POD/host interface.
The content information is transmitted in a so-called transport stream, which contains several elementary streams. An elementary stream may contain a video feed, a sound track or a data file. Copy protection is provided on the basis of elementary streams.
For every copy protected elementary stream, there is an associated Copy Control Information (CCI). It is used by the host device to decide (1) how many copies (e.g. one copy, zero copies) of the elementary stream can be made; (2) what copy formats are allowed (e.g. analog formats including composite and component and digital formats); and (3) other copy protection related activities. The CCI is passed from the POD module to the host device to indicate how the corresponding elementary stream of the content should be treated. To prevent an “intruder” from tampering with the CCI, it must be protected when transmitted to the host device.
Standard cryptographic methods exist for the general encryption/decryption within such a system, however, these methods each have significant limitations. In one such method a proprietary CA system, as well as its associated algorithms for encryption/decryption, is used. Instead of transmitting every CCI associated with an elementary stream in the content, this method transmits the most restrictive CCI to the host.
Although, the CCI is not encrypted when transmitted between the POD module and the host device, it is afforded some degree of protection. The CCI is typically embedded in shared keys that are used to encrypt the content information at the POD module and decrypt the content information when received by the host device.
One problem with this approach is that if the content contains multiple elementary streams, each elementary stream may have a different CCI. Since the host device uses the most restrictive CCI for its copy protection processing, content information may be prevented from being properly copied. For example, if there are two elementary streams, and the CCI associated with the first one indicates “copy once”, while the CCI associated with the second one indicates “never copy”, then neither of the elementary streams can be copied. This prevents a stream from being legally copied when another (possibly unrelated) stream has a more restrictive CCI.
Thus, there is a clear and present need for an effective means to provide copy protection that utilizes encryption, while still providing consumers with the information desired in a less restrictive manner. In particular, copy protection of information between a POD module and a set-top box.